Piercing point



March 13, 1934. .1. J. DUNN ET AL PIERCING POINT Filed Feb. 23, 1932 m mr nWN 2 @M 1m WH. L

Patented Mar. 13, 1934 UNITED STATES PATENT OFFICE I PIERCIN G POINT Application February 23, 1932, Serial No. 594,730 2 Claims. (01. 78- 103) This invention relates to piercing points used in the manufacture of seamless tubing, and has for its object the provision of a novel form of piercing point adapted to be water-cooled while in use.

Since the early stages of the development of the seamless tube art the mills have used a tubular bar to hold the piercer point in the piercing mill while piercing the solid billet from which 10 the tube is formed. The tubular blank or shell formed from the billet fits over the point onto the piercer bar or mandrel, heating the bar or mandrel to a high temperature, especially on the rapid working of the mills in use at the present time. The piercer bar or mandrel must,

therefore, be cooled internally by water to maintain its strength and to prevent frequent mill shut-downs to change bars. nearest the piercer is closed with a solid forging or casting known as the bar plug or cap, which plug or cap is threaded into the end of the bar and serves to support the piercer point.

The piercer point heretofore in general use has been a solid steel casting or forging which is mounted on the bar or cap. During the piercing operation this solid piercing point gets excessively hot and must be removed after each billet has been pierced, and a fresh point pressed on the bar plug to start the next billet.

The heated solid points are cooled in a waterbosh before being used again, and generally may be used for piercing from twenty-five to fifty billets before being scrapped. Frequently, when piercing long lengths or very light walled tubing,

the service obtained from the solid point is very poor and results in the production of a high percentage of defective pipe.

Attempts have been made to overcome the objections to the solid piercing points of the prior art by the use of special alloys and points formed of a combination of metals. However, such attempts have failed to materially improve the piercing points.

Experience has shown the art, however, that the main objections to the prior art points have resulted from the inability to dissipate heat from the piercing points. The present invention, therefore, provides a hollow water-cooled piercing point which will remain sufficiently cool, during the piercing operation, for continuous use on successive piercing operations without becoming heated to such a degree that its usefulness will be affected.

In order that a water-cooled piercer point may be successful in operation it is necessary that The end of the bar the mandrel or piercer bar, the bar plug or cap and the piercer points all be water-tight and rigidly held together. It is also necessary that the parts be so designedand constructedthat they will withstand the extreme forces to which they will be subjected during the piercing operations. The piercer point construction of this application is adapted to answer all the requirements set forth above.

In the drawing:

Figure l is a sectional plan through a piercing point constructed in accordance with this invention.

Figures 2 and 3 are sectional elevations taken on the lines II--II and III-III of Figure 1. Referring more particularly to the drawing,

the numeral 1 designates the mandrel or piercer bar, which is of tubular construction and has a threaded connection with one end of a hollow bar plug or cap 2 which may be formed of a steel casting or forging. The piercer point is designated generally by the numeral 10 and is of hollow construction. The point may also be formed from a suitable steel forging or casting.

The bar or plug 2 is provided with a tapered end or nose 2 which is machined and ground to a smooth finish and fitted within the rear end of the piercer point 10. The interior surface of the point 10 is tapered inwardly from the rear end toward the nose end thereof for a length at least equal to the tapered end 2 of the bar plug 2 forming a sleeve portion 5. The point 10 is adapted to have a driving fit with the end 2 of the plug 2 and, therefore, the sleeve portion 5 has a machined and ground finish similar to the end 2 of the plug 2, and when the plug is forced onto the portion 2 of the plug 2 a water-tight joint is formed between the sleeve portion 5 of the point 10 and the end 2 of the plug 2. The interior of the point forward of the sleeve portion 5 is provided with a plurality of longitudinally extending flutes forming longitudinal fins or ribs 6, which serve the dual purpose of strengthening the point and also provide an increased surface for dissipating the 0 heat from the point.

The fins 6 terminate short of the nose end of the point and the side walls of the point are thinnest between the fins or ribs. The thin wall sections between the fins or ribs 6 are made possible due to the supporting or strengthening action of the fins or ribs, and such thin sections aid materially in maintaining the point cool during the piercing operations.

The end pressure on the piercer point during the piercing operation N. .w to tighten the connection or joint between'the point 10 and the end 2 of the plug 2 and effectively prevent the leakage of water from the point assembly. It is also necessary that the bar plug or cap metal and piercer point metal have the same coefficient of expansion in order that the joint between the cap or plug 2 and the point 1 may stay tight during the use of the piercer point The plug or cap 2 is bored longitudinally to provide a water passage from the bar 1 into the point 10, and a water-circulating pipe 3 projects through the bar 1 and plug 2 into the point to a location adjacent the nose end of the point.

The pipe 3 is of less diameter than the bore 4 in the plug or cap 2 so as to provide an opening in the cap or plug 2 surrounding the pipe 3 having an areaat least equal to that of the bore of the pipe 3. The incoming water passes through the pipe 3, impinges upon and washes the whole inside surface of the point, bar cap or plug and bar 1, cooling all three units in an effective manner.

Due to the fact that the space around the pipe 3 in the cap 2 and bar 1 is at least equal in cross-sectional area to the cross-sectional area of the bore in the pipe 3, a free and uniform flow of water through the assembly takes place. Therefore, a suificient water pressure is not built up to disrupt the connection between the point 10 and the plug or cap 2. The wall thickness of the piercerpoint must be carefully regulated to give the requisite strength, and also be as thin as possible for rapid cooling. For small points between two inches and five inches outside diameter, the best thickness, so far as present experience has shown, should be approximately one-eighth of the outside diameter of the point, and for points ranging from five inches to eight inches outside diameter a wall thickness of three-fourths of an inch has proved most satisfactory.

While we have shown and described one speciflc embodiment of our invention, we do not wish to be limited thereto, since various modifications may be made without departing from the scope of our invention, as defined by the appended claims.

We claim:

1. A piercing point adapted for water-cooling comprising in combination a bar plug portion having a bore extending longitudinally therethrough, a tapered end projecting from said plug and having a ground finish and a hollow point having a tapered and ground finished sleeve portion extending inwardly from its rear end an appreciable distance toward the nose end thereof and adapted to receive said tapered end of said plug, said point having a driving fit with said plug and a plurality of fins projecting inwardly from the interior surface of said point and extending longitudinally of said point from said sleeve portion forwardly to a pointadjacent the nose end of said point.

2. The combination with a tubular bar member, of a bar plug provided with reduced end portions and having a bore extending longitudinally therethrough, one end ofsaid plug being threaded into said bar and the other end being tapered and having a ground finish, a hollow point having a tapered and ground finished sleeve portion extending inwardly from its rear end an appreciable distance and adapted to receive said tapered end of said plug, said point having'a driving fit with said plug, a plurality of fins projecting inwardly from the interior surface of said point and extending longitudinally thereof from said sleeve portion toward the nose end of said point member, and a water-circulating pipe extending through said tubular bar and bar plug into said point, the bore of said bar and bar plug being of such size that the space around said pipe'will have a cross-sectional area at least equal to the cross-sectional area of the interior bore of said pipe.

JOHN J. DUNN.

EDWIN C. WRIGHT. 

